My vertical 3 band QRP antenna for portable use on 40m, 20m and 30m
 

The antenna mounted on a 8m fibreglass mast during a SOTA activation

Doing a lot of portable QRP activity for SOTA and GMA I repeatedly ended up on summits with no trees or structures to mount a 40 or 20m dipole QRP antenna like my self built lightweight 20m dipole for SOTA. I already own a 8m HD fibreglass mast and was doing some research for a vertical antenna with no need for a second mount point.

The antenna during testing

Solution

After some research I ended up with a solution suggested by N2CX (as far as I found out, there might be another initial inventor which should be credited) and now produced commercially also by http://qrpguys.com/. It is a very basic construction made up from around 6m of vertical wire and 4 ground rods with 2 toroid coils in line for 40m (coil no. 1 and coil no. 2 active), 30m (only coil no. 2 active) and 20m (no coil active).  A basic description can be found here.

This is my implementation of it

• I added a 1:1 current balun made from FT140-43 and RG174 coaxial wire.
• The coils, the switches and the balun was fitted into a small plastic case
• The connectors for the antenna wire and the ground rods were mounted outside of the plastic case for easier assembling

My radials have fixed length of 3 meters.

Please find a few photos of my construction below. 73 de Alfred

The case with the PL connector for the antenna, the coils and the switches. Here without the 1:1 balun which I added later

In order to attach the antenna and ground rods I mounted 4mm (I think) screws outside the case